Yes, the valve used for the seat.
It would be interesting if your design could be modified in a way that would be workable for both the Boston Valve and these seat valves.
Carrying multiple adapters isn’t practical when using these boats for something like portage backpacking. Too easy to lose small accessories.
I bet a similar design without the air windows and maybe a slight modification to the nozzle tip would do the trick. What do you think?